This invention relates to a hybrid vehicle, and in particular, to a warm-up of a battery.
A hybrid vehicle is a vehicle driven by a motor, and the required power is supplied from a generator driven by an engine. The engine is operated in a high fuel efficiency operating region as much as possible. The battery is charged by the excessive power generation and energy recovered when the vehicle decelerates. When the required driving force is large, power is supplied to the motor also from the battery.
The input/output characteristics of the battery depend on the battery temperature, and charging/discharging capability is restricted the more the battery temperature falls. Therefore, the performance of hybrid vehicles is largely influenced by the battery temperature, and the battery must be maintained at the proper temperature.
In JP2000-92614A published by the Japanese Patent Office in 2000, when battery temperature is low, charge and discharge of the battery is performed forcibly such that current passes through the battery. Heat is generated due to the internal resistance of the battery, and thus the battery is heated from inside. Specifically, when the present charge state of the battery has not reached the maximum charge state, the battery is charged, and the battery is discharged once the maximum charge state is reached.
However, this warm-up of the battery may also be performed when the vehicle is running, and if this is done during running of the vehicle, the engine rotation speed may change regardless of the driver""s intention due to the charging/discharging of the battery, and may give the driver an uncomfortable feeling.
In order to charge the battery, the engine is operated at a larger output than the output required to drive the vehicle, and the power for charging is generated by the excess output. However, the power for charging varies with the charge state of the battery, and thus the output which is required of the engine also varies according to the charge state of the battery. If a large current is passed through the battery, warm-up of the battery is faster, but if an excessive current is passed, the life of the battery will be shortened, so it is desirable to charge with the maximum power which the battery can receive (power which can be input). For this reason, the target charging power is set according to the charge state of a battery. Also, the maximum power which can be output from the battery when discharging is performed is also determined according to the charge state of the battery.
As a result, when temperature control of the battery is performed, the target engine output varies regardless of the driver""s intention, and the controlled engine output therefore varies accordingly.
In general, in a hybrid vehicle, to obtain the target engine output, as the operating point is determined by a combination of engine rotation speed and engine torque which gives the best engine efficiency at that output, if an engine output is varied as mentioned above, the engine rotation speed will also change accordingly, and an uncomfortable feeling will be imparted to the driver.
Moreover, if there is a change from charge to discharge or conversely due to battery temperature control, the target engine output will vary in a step manner. Thus, during engine output control accompanied by a variation of engine rotation speed, a response delay in the actual output occurs, and a discrepancy is produced between the target charging power and actual charging power.
It is therefore an object of this invention to prevent change of engine rotation speed during warm-up control of the battery, and prevent an uncomfortable feeling during driving.
In order to achieve above object, this invention provides a hybrid vehicle which includes a generator, an engine which drives the generator, a motor which drives the vehicle and a battery connected to the generator and motor, and performs Electric Vehicle (EV) running wherein the vehicle runs under the motor driven with electric power stored in the battery without operating the engine, and Hybrid Electric Vehicle (HEV) running wherein the engine is operated and the vehicle runs under at least one of the engine and the motor, comprising an external charge device which charges the battery using an external power supply, a map information device which includes map data and recognizes the present position of the vehicle on the map data, and a controller. The controller functions to register a point at which the external power supply is installed in the map data in the map information device as a base point, register an EV running area centered on the base point in the map data in the map information device, increase the charge value of the battery beforehand during HEV running before arriving at the EV running area, when the vehicle runs towards the base point from outside the EV running area, and switch to EV running when the vehicle enters the EV running area.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.